The present invention generally relates to semiconductor devices, and, more particularly, to lead frames used to assemble semiconductor devices.
Leaded semiconductor devices have leads that extend from a main package body. Non-leaded devices, such as Quad Flat No-leads (QFN) devices, are similar to leaded semiconductor devices except that the leads do not extend outwardly or project from the package body. Rather, the leads are generally flush with the package body. Both leaded and non-leaded devices are assembled using lead frames. Lead frames are metal frames that typically include a die mounting pad (i.e., a die pad or die flag), and a plurality of leads that surround the die pad. Lead frames are provided in strip or array form so that many devices may be assembled simultaneously.
FIG. 1 shows a portion of a lead frame array 10, where two lead frames 12 are shown. The lead frames 12 include central die pads 14 that are rectangular in shape. Leads 16 are provided along two of the opposing sides of the die pads 14. The leads 16 that are located between the die pads 14 of the two lead frames 12 are joined by a connection bar 20, or put another way, the leads 16 project outwardly from the connection bar 20 that extends between the two lead frames 12. After semiconductor dies (outlies of the dies are shown in dashed lines) are attached to the die pads 14 and electrically connected to the leads 16, either before or after a molding process in which the dies and electrical connections are covered with a molding compound, the assembled devices are separated by cutting along the connection bar 20. Because the connection bar 20 is made of metal, there is considerable wear on the saw blades used to singulate the assembled devices.
FIG. 2 is an enlarged view of a portion of a connection bar 20 with leads 22 extending outwardly from two opposing sides thereof. The connection bar 20 has been etched so that it is thinner than the leads 22, making it easier to saw and allowing for less wear on the saw blade. However, etching of the connection bar 20 also weakens the connection bar 20 such that it is susceptible to bending, as shown in the circled portion of FIG. 3. This bending moves the leads 22, which can cause lead shorting and/or wire bonding issues. Accordingly, it would be advantageous to have a lead frame that is strong, yet allows for a long saw blade life.